Abaixo está uma instrução que descreve uma tarefa de geração de SQL, combinada com uma entrada que fornece mais contexto sobre os esquemas de tabela disponíveis. Escreva o código SQL que responda adequadamente à solicitação
 ###Instrução: Quantas escolas têm uma matrícula de 850?
 ###Tabelas: CREATE TABLE invercargill_city (invercargill_city_id AUTO_INCREMENT PRIMARY KEY, Name VARCHAR, Gender VARCHAR, Area VARCHAR, Authority VARCHAR, Decile INT, Roll INT) CREATE TABLE connecting_links (connecting_links_id AUTO_INCREMENT PRIMARY KEY, County VARCHAR, Name VARCHAR, Length (miles) INT, West or south terminus VARCHAR, East or north terminus VARCHAR) CREATE TABLE backcountry_zones (backcountry_zones_id AUTO_INCREMENT PRIMARY KEY, Area VARCHAR, Name VARCHAR, Zone VARCHAR, Group(s) INT, Parties INT, Max People INT, Camp Type VARCHAR) CREATE TABLE grp_lists (grp_lists_id AUTO_INCREMENT PRIMARY KEY, Rank (2008) INT, Federal Subjects VARCHAR, Russian Name VARCHAR, 2008 (RUB) INT, 2008 (USD) INT, 2007 (RUB) INT, 2007 (USD) INT, 2005 (RUB) INT, 2005 (USD) INT) CREATE TABLE participating_schools (participating_schools_id AUTO_INCREMENT PRIMARY KEY, School VARCHAR, Location VARCHAR, Enrolment INT, Founded INT, Denomination VARCHAR, Day/Boarding VARCHAR, School Colours VARCHAR, Abbreviation VARCHAR, In competition since INT)  
SELECT COUNT Founded FROM participating_schools WHERE Enrolment = 850